Absence of chiral symmetry breaking in multi-flavor strongly coupled lattice gauge theories

We consider lattice gauge theories at strong coupling with gauge group U(N-C), or SU(N-C) restricted to the meson sector, and coupled to N-F flavors of fundamental representation staggered fermions. We study the formation of a chiral condensate by means of resummation of a hopping expansion. Different classes of graphs become dominant as the parameter (N-F/N-C) is varied. By performing graph resummation we obtain an equation for determining the condensate as a function of (N-F/N-C) and mass m. For values of (N-F/N-C) below a critical value, one reproduces the well-known result of the existence of a nonvanishing condensate solution in the m = 0 limit. Above the critical (N-F/N-C) value, however, no such solution exists, its abrupt disappearance indicating a first-order transition to a chirally symmetric phase with composite (colorless) excitation spectrum. DOI: 10.1103/PhysRevD.87.034513